SMTP sender application on port 587

Alt198

Dear community,

I am trying to a SMTP sender, but everytime I try to use port 587 with TLS or StartTLS I get an authentication failiure. I have checked box "Allow SMTP sending (used by POP3/IMAP clients)" for the user. Unencrypted sending over port 25 works OK, but once TLS is switched on and port 587 selected, authentication failiure.

Any help would be appriciated,
Thank you

Alf06

Alt198 did you set up the cert / key files for postfix smtpd?

WalterH

Do you see errors or useful information in journalctl -f?

jengelh

From Linux, openssl s_client -connect xyz:587 -starttls smtp can be used to diagnose TLS issues.